1. Field of the Invention
The present invention relates to a metal working oil composition, and more particularly to a metal working oil composition, which is suitable for metal working processes such as cutting and grinding.
2. Description of the Related Art
Generally speaking, in metal working processes such as cutting and grinding, chlorine-based extreme pressure agents have been used because of their excellent ability to improve cutting performance and relatively low cost.
However, in recent years, water-insoluble cutting fluids containing chlorine-based extreme pressure agents have been criticized as responsible for corrosion and damage of incinerators caused by environmental pollution and emission of chlorine gases, as dioxin is generated during incineration of waste.
Moreover, chlorinated paraffins, a class of chlorine-based extreme pressure agents, raise some concern about their toxicity and carcinogenicity.
In view of the foregoing, there have been developed oil compositions that do not contain chlorine-based extreme pressure agents.
For example, Japanese Patent Application Laid-Open (kokai) Nos. 6-313182 and 6-330076 disclose cutting oil compositions containing a sulfonate of an alkali metal and/or an alkaline earth metal. However, the cutting oil compositions actually disclosed in those publications--although applicable to turning and boring--are problematic when used in low-speed, heavy cutting in which the cutting speed is not more than 40 m/min.; e.g., broaching or gun-drilling, as they induce breakage of tools due to cutting force unless considerable amounts of such compositions are used or the working conditions are set to extremely mild.